DOI: 10.1002/chem.201103226

Synthesis, Structure, Spectroscopic, and Electrochemical Properties of HighlyFluorescent Phosphorus(V)–meso-Triarylcorroles

Avijit Ghosh and Mangalampalli Ravikanth*[a]

Introduction

Corroles are tetrapyrrolic macrocycles, like porphyrins, butwith one less carbon atom at their periphery and one extrainner NH proton.[1] They are also 18-p-electron systems andpossess aromaticity like porphyrins and other related por-phyrinoids. Moreover, like porphyrins, these macrocyclespossess very interesting ground- and excited-state properties,and hence can be used as substitutes in the place of porphyr-ins.[2] Although corroles have been known for more thanthree decades, up until 1999, their synthesis was very diffi-cult. In 1999, Gross et al.[3] and Paolesse et al.[4] independ-ently published simple procedures to synthesize corrolesfrom commercially available starting materials. These proce-dures helped to enhance the research into corroles and sev-eral new types of corroles and their applications have beenreported in recent times.[5] Because of their �3 charge, thesetetrapyrrolic contracted-macrocycles stabilize metals in

higher oxidation states,[6] unlike porphyrins which have a �2charge. The literature on transition-metal corroles[7] is exten-sive and numerous comparisons have been made with por-phyrins that contain the same transition-metal ion. In con-trast, there are only a few examples of corrole-stabilizedmain-group ions[8] and, specifically, to the best of our knowl-edge, there are only three reports in this regard with PV–cor-role complexes.[9] Paolesse et al.[9a] reported the synthesis ofthe first PV–corrole complex (I), a pentacoordinated com-plex as confirmed by X-ray crystallography, by heating 8,12-diethyl-2,3,7,13,17,18-hexamethylcorrole and POCl3 at refluxin pyridine (Scheme 1). Kadish, Guilard, Vogel, and co-workers[9b] reported the synthesis of a PV complex of2,3,7,8,12,13,17,18-octaethylcorrole and used it as precursorfor the synthesis of axially substituted hexacoordinate PV

complexes. Gross and co-workers[9c] reported the synthesisof a hexacoordinated PV complex of 5,10,15-tris(pentafluor-ophenyl)corrole (II), which is the only reported PV complexof meso-triarylcorrole (Scheme 1). Here, we report the syn-thesis, characterization, X-ray structure, electrochemical,and photophysical properties of a series of PV complexes ofmeso-triarylcorroles (1–7; Scheme 2). The spectroscopic andelectrochemical studies indicated that compounds 1–7 exhib-ited quite different and interesting properties compared toPV–meso-tetraarylporphyrins, such as 5,10,15,20-tetraphenylporphyrinato ACHTUNGTRENNUNG(TPP)-phosphorus(V) dihydroxide([P ACHTUNGTRENNUNG(TPP)(OH)2]

+; III).[10]

Abstract: The synthesis, spectroscopic,and electrochemical properties ofseven new PV–meso-triarylcorroles (1–7) are reported. Compounds 1–7 wereprepared by heating the correspondingfree-base corroles with POCl3 at refluxin pyridine. Hexacoordinate PV com-plexes of meso-triarylcorroles were iso-lated that contained two axial hydroxygroups, unlike the PV complex of 8,12-diethyl-2,3,7,13,17,18-hexamethylcor-role, which was pentacoordinate, or thePV complex of meso-tetraphenylpor-phyrin, which was hexacoordinate withtwo axial chloro groups. 1H and31P NMR spectroscopy in CDCl3 indi-cated that the hexacoordinated PV–

meso-triarylcorroles were prone toaxial-ligand dissociation to form penta-coordinated PV–meso-triarylcorroles.However, in the presence of stronglycoordinating solvents, such as CH3OH,THF, and DMSO, the PV–meso-triaryl-corroles preferred to exist in a hexa-coordinated geometry in which the cor-responding solvent molecules acted asaxial ligands. X-ray diffraction of twocomplexes confirmed the hexacoordi-nation environment for PV–meso-triar-

ylcorroles. Their absorption spectra intwo coordinating solvents revealed thatPV–meso-triarylcorroles showeda strong band at about 600 nm togetherwith other bands, in contrast to PV–por-phyrins, which showed weak bands inthe visible region. These compoundswere easier to oxidize and more diffi-cult to reduce compared to PV–por-phyrins. These compounds were bright-ly fluorescent, unlike the weakly fluo-rescent PV–porphyrins, and the quan-tum yields for selected PV–corroleswere as high as AlIII and GaIII corroles,which are the best known fluorescentcompounds among oligopyrrolic mac-rocycles.

Keywords: corroles · electrochem-istry · fluorescence · meso com-pounds · phosphorus

[a] A. Ghosh, Prof. M. RavikanthDepartment of ChemistryIndian Institute of Technology, Bombay, PowaiMumbai 400 076 (India)E-mail : ravikanth@chem.iitb.ac.in

Supporting information for this article is available on the WWWunder http://dx.doi.org/10.1002/chem.201103226.

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Results and Discussion

The insertion of phosphorus into tetrapyrrolic macrocycles,such as porphyrins[10] and corroles,[9] has typically been car-ried out by heating the free-base macrocycles with variousreagents, such as PCl3, PCl5, and POCl3, at reflux in pyri-dine. However, recently, POCl3 has become the more-com-monly used reagent compared to the other two. We testedthe phosphorus-insertion into free-base corroles by taking5,10,15-triphenylcorrole, [H3ACHTUNGTRENNUNG(TPC)], as a reference com-pound and independently reacting it with all three common-ly used reagents in refluxing pyridine. The progress of thereaction was followed by TLC on silica gel and by absorp-tion spectroscopy. Initially, the reaction mixture was greenin color but, as the reaction progressed, the color changed

to a bright pink–violet witha slight greenish tint. The ab-sorption data, taken at regularintervals, indicated that absorp-tion bands corresponding toa PV complex of meso-triaryl-corrole (1) started to appearafter 5 min and the reactionwas complete within 15–30 min,depending on the reagent. Thereaction was very fast whenPOCl3 was used as the reagent.Excess reagent and pyridinewere removed under reducedpressure and the crude com-pound was subjected to columnchromatography on alumina toafford compound 1 in 78 %yield. Compound 1 was alsostable to column chromatogra-phy on silica gel. Although thereaction proceeded smoothlywith all three phosphorus re-agents, the six other PV deriva-tives (2–7) were all prepared byusing POCl3 under similar con-ditions (Scheme 2). For compar-ison purposes, we also preparedknown PV–porphyrin complexIII (Scheme 1) by using POCl3

in refluxing pyridine.[10b] How-ever, phosphorus-insertion intothe porphyrin was very slowand required heating overnight.In this reaction, the hexacoordi-nated complex [PACHTUNGTRENNUNG(TPP)Cl2]

+ in-itially contained two axial chlo-ride ions, which, on furtherheating with aqueous pyridineat reflux followed by columnchromatography on silica gel,transformed into compound III,with two axial hydroxy groups,

as reported previously.[10b] Interestingly, spectroscopic analy-sis (see below) indicated that compounds 1–7 were alsohexa-coordinated but contained two axial hydroxy ligands.Thus, we concluded that complexes 1–7, with two axial hy-droxy groups, were more stable to isolation than the PV–meso-triarylcorroles that contained two axial chloride li-gands. Complexes 1–7 were soluble in common organic sol-vents and were characterized by MS and various other spec-troscopic techniques. The HRMS spectra of compounds 1–7showed molecular-ion peaks that corresponded to hexacoor-dinate species, as well as [M�17]+ peaks that correspondedto pentacoordinate species, which may have been formed bythe loss of one axial OH group (see the Supporting Informa-tion, S4–S10).

Scheme 1. Previously reported PV–corrole complexes (I and II) and a PV complex of a porphyrin analogue(III).

Scheme 2. Synthesis of compounds 1–7.

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NMR spectroscopy : The composition of compounds 1–7 wasconfirmed by detailed NMR spectroscopic studies. 1H and31P NMR spectroscopic techniques were very useful forjudging the coordination number of the phosphorus center.A comparison of the 1H and 31P NMR spectra of compound1 with those of analogous phosphorus–porphyrin complexIII recorded is shown in Figure 1. In compound III, the

eight pyrrole protons appeared as a broad singlet, whereasin compound 1, the eight pyrrole protons appeared as eightsets of doublet of doublets. At first, this result was very con-fusing. However, we realized that the intensity of the eightsets of pyrrole signals varied when we recorded the1H NMR spectra of compounds 1–7 after different lengthsof time. For instance, a freshly prepared sample of com-pound 5 showed four intense sets of signals and four less-in-tense sets of signals. However, after being left to stand inCDCl3, the same compound showed eight sets of signals ofequal intensity (see the Supporting Information, S22 andS23). Furthermore, the 1H NMR spectra of compounds 2, 6,and 7 (in CDCl3), which contained electron-withdrawinggroups on the meso-phenyl rings, showed predominantlyfour sets of doublet of doublets, with almost negligible in-tensity of other four sets of signals (see the Supporting In-formation, S25). These results indicated that compounds 1–7

may have existed in a hexacoordinate geometry but wereprone to ligand-dissociation to form pentacoordinate spe-cies. To confirm the presence of penta- and hexacoordinatespecies in solution, we recorded the 31P NMR of compounds1–7. It is well-established[11] that the chemical shifts of phos-phorus nuclei in 31P NMR spectroscopy are sensitive to thecoordination number of the phosphorus center, and detailed31P NMR studies on phosphorus derivatives of porphyrins,phthalocyanines, and related macrocycles have indicatedthat hexacoordinate phosphorus macrocycles typically showsignals in the range d=�180 to �200 ppm, whereas penta-coordinate compounds typically show signals in the ranged=�90 to �110 ppm. In the 31P NMR spectra (CDCl3),compound 1 showed two signals of almost equal intensity atd=�100.7 and �191.5 ppm, which corresponded to thepenta- and hexacoordinate species, respectively. However,compounds 2, 6, and 7, which contained electron-withdraw-ing substituents on the meso-phenyl groups, showed an in-tense signal at about d=�200 ppm and a much less intensesignal at about d=�100 ppm (see the Supporting Informa-tion, S25), thus indicating that these complexes were rela-tively more stable in their hexacoordinate environment, andunderwent very slight axial-ligand-dissociation to form pen-tacoordinate species. Thus, 1H and 31P NMR studies of com-pounds 1–7 in CDCl3 indicated that these complexes pre-ferred to exist as hexacoordinated species but were prone toaxial-ligand-dissociation. This result suggested that the axialhydroxy groups were weakly bound to the central PV ionand could readily dissociate in solution. At this juncture, itwas clear that if we replaced the hydroxy group with anyother strongly coordinating group then these PV–corrolecomplexes may have preferred to exist in their hexacoordi-nated geometry. To test this hypothesis, we carried out titra-tions of compound 1 (in CDCl3) with increasing amounts ofCH3OH (in CDCl3); the changes in the 1H and 31P NMRspectra are shown in Figure 2 and Figure 3, respectively. Theaddition of CH3OH clearly resulted in the formation of hex-acoordinate species by replacing the weakly bound axialOH ligands with more strongly bound OCH3 ligands. Thisresult was reflected in the reduction of eight sets of b-pyr-role signals to form four sets of signals in the 1H NMR spec-tra (Figure 2) and in the disappearance of a signal at d=

�100.7 ppm in the 31P NMR spectra that corresponded tothe pentacoordinate species (Figure 3). Thus, the systematicaddition of CH3OH to compound 1 in CDCl3 resulted in thegradual disappearance of four sets of doublet of doublets(d=9.38, 9.20, 9.13, and 8.88 ppm), which corresponded tothe pentacoordinate species, and the simultaneous increasein the intensity of the other four sets of doublet of doublets(d=9.25, 9.05, 8.96, and 8.79 ppm) in the 1H NMR spectrum(Figure 2). Furthermore, during our systematic 31P NMR ti-tration (Figure 3), we noted the possible existence of fourintermediate species in solution: one pentacoordinate spe-cies, [P ACHTUNGTRENNUNG(TPC)(OH)]+ (type a), and three hexacoordinate spe-cies, [P ACHTUNGTRENNUNG(TPC)(OH)2] (type b), [P ACHTUNGTRENNUNG(TPC)(OH) ACHTUNGTRENNUNG(OCH3)](type c), and [P ACHTUNGTRENNUNG(TPC) ACHTUNGTRENNUNG(OCH3)2] (type d; Scheme 3). As men-tioned above, in CDCl3, compound 1 showed two signals in

Figure 1. Comparison of 1H NMR spectra (a, b) and the 31P NMR spectra(c) of compounds 1 and III in CDCl3 at room temperature.

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A. Ghosh and M. Ravikanth

the 31P NMR spectrum (d=�100.7 and �191.5 ppm), whichcorresponded to the type-a and type-b complexes, respec-tively. On addition of one equivalent of CH3OH to com-pound 1 in CDCl3, a gradual decrease in the intensity of thesignal at d=�100.7 ppm (type a species) as well as a de-crease in the intensity of the signal at d=�191.5 ppm (type-b species) were noted, together with the appearance ofa new signal at d=�184.1 ppm (hexacoordinate type-c spe-cies). On addition of two equivalents of CH3OH, we ob-served a third hexacoordinate signal at d=�176.9 ppm(type-d species) in addition to the two signals at d=�184.1and �191.5 ppm, which corresponded to other hexacoordi-nate complexes (type b and type c, respectively). On furtherincrease in the number of equivalents of CH3OH, the signalsthat corresponded to the pentacoordinate complex (type a,d��100.7 ppm) and two of the hexacoordinate complexes(type c and type d, d��184.1 and �191.5 ppm, respectively)gradually disappeared, whereas the signal that correspondedto the hexacoordinate complex of type d (d��177.1 ppm)increased in intensity. In the presence of excess CH3OH,only the signal at d=�177.3 ppm (type d) was observed,thereby indicating that the complex was now hexacoordinatewith two OCH3 groups as axial ligands. Furthermore, thisresult was also clearly evident in the gradual disappearanceof the signal that corresponded to the axial OH proton (d=

�4.64 ppm) and the appearance of a doublet at d=

�2.47 ppm, which corresponded to the axial OCH3 protonsin the 1H NMR spectra, thus confirming the substitution ofthe axial OH groups by OCH3 groups (see the SupportingInformation, S11). The existence of complex 1 as a hexacoor-dinate species in coordinating solvent was further verifiedby 31P NMR spectroscopy in pure CD3OD, which showedone signal at d=�178.0 ppm and also by 1H NMR spectros-copy, which showed four sets of doublet of doublet at d=

9.38, 9.03, 8.95, and 8.78 ppm. Similarly, in other strongly co-ordinating solvents, such as [D6]DMSO and CD3CN, com-plex 1 existed as a hexacoordinate species and showed foursets of pyrrole signals that were more upfield shifted com-pared to compound 1 in CD3OD. For example, the four setsof pyrrole signals for compound 1 in CD3OD (d=9.38, 9.03,8.95, and 8.78 ppm) were shifted upfield to d=9.30, 8.96,8.87, and 8.68 in CD3CN and to d=9.19, 8.80, 8.69, and8.58 ppm in [D6]DMSO (see the Supporting Information,S21). The 31P NMR spectra also showed only one signal atd��190 ppm in both of these coordinating solvents, whichfurther supported the hexacoordination of compound 1. Wealso recorded 1H and 31P NMR spectra of compound 1 inCDCl3 in the presence of excess amounts of other coordinat-ing solvents, such as THF, which also confirmed the hexa-

Figure 2. 1H NMR titration of compound 1 with CH3OH in CDCl3 atroom temperature.

Figure 3. 31P NMR titration of compound 1 with CH3OH in CDCl3 atroom temperature.

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FULL PAPERHighly Fluorescent Phosphorus(V)–meso-Triarylcorroles

coordinate environment of compound 1 (see the SupportingInformation S19 and S20). Although the pyrrole signalswere very useful for identifying penta- and hexacoordinatespecies, the meso-aryl signals exhibited minimal changes intheir chemical shifts between the two environments, andwere not helpful in identifying the coordination environ-ment (see the Supporting Information, S12). Thus, ourNMR studies clearly indicated that compounds 1–7 pre-ferred to exist in the hexacoordinate geometry with twoidentical axial ligands in strongly coordinating solvents.

Crystallographic characterization : Further confirmation ofthe formation of compound [PACHTUNGTRENNUNG(TPC) ACHTUNGTRENNUNG(OCH3)2] was providedby single-crystal X-ray crystallography. Figure 4 showsORTEPs of compound 1. Compound 1 was crystallized byslow diffusion of n-hexane into a solution of compound 1 inCH2Cl2/benzene (3:1) in the presence of CH3OH, overa period of one week. Compound 1 crystallized in the ortho-

rhombic space group P21. Thecrystal data and data collectionparameters are summarized inTable 1. To the best of ourknowledge, compound 1 is thefirst PV–meso-triarylcorrole tobe characterized by single-crys-tal X-ray analysis; the onlyother reported crystal structureof a phosphorus–corrole com-plex was that of pentacoordi-nate compound I (Scheme 1).[9a]

Compound 1 crystallized asa hexacoordinate complex withOCH3 groups as axial ligands.The central phosphorus atomwas almost in the plane definedby the four nitrogen atoms ofthe pyrrole rings, unlike com-pounds I and III, respectively.In compound I, the pentacoor-dinate phosphorus atom laymore than 0.4 � out of themean corrole plane towards theoxygen atom of the axial hy-droxy ligand. This kind of out-of-plane displacement of thecentral atom of metalloporphyr-ins[12] or metallocorroles[6,13] iscommonly observed for penta-coordinate complexes. Similarly,in case of compound III, thehexacoordinate central phos-phorus atom was displaced by0.09 � from the mean plane ofthe pyrrole nitrogen atoms. Fur-thermore, the P�O bondlengths were inequivalent incompound III, whereas in com-pound 1, the P�O bond-lengths

(P�O1 1.668 �, P�O2 1.663 �) were equivalent and were inthe same range as those found in other analogous PV–meso-tetraarylporphyrin complexes.[10b,c,e] The four P�N distanceswere inequivalent in compound 1 and the average P�Nbond length (1.83 �) was slightly longer than the averageP�N bond length (1.80 �) in compound I. However, theaverage P�N distances in both PV–corrole complexes I and1 were shorter than that in compound III (1.89 �)[10a,e] aswell as the average M�N distance in other metal complexesof meso-triarylcorroles reported.[7,8] Moreover, compound1 was more planar than its corresponding free-base cor-role[14] and metallocorroles.[15] In the free-base corrole, thethree inner NH protons caused steric crowding, thereby re-sulting in strain in the corrole macrocycle. On complexationwith small PV ions, the strain imposed by the inner NH pro-tons was released and the corrole ring became more planarin compound 1. Furthermore, in compound 1, the opposite

Scheme 3. All of the possible intermediate complexes during the NMR titration of compound 1 with CH3OHin CDCl3 at room temperature.

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A. Ghosh and M. Ravikanth

meso-phenyl groups were placed in mutually oppositeplanes compared to the mean corrole plane, with average di-hedral angles of 518 and 548. The other meso-phenyl groupwas almost perpendicular (dihedral angle �908) to themean plane of corrole ring. Interestingly, a weak hydrogen-bonding interaction was observed between the oxygenatoms of the axial OCH3 groups and the hydrogen atoms ofone of the meso-phenyl group of another molecule, therebyresulting in the formation of a supramolecular 2D network(see the Supporting Information, S35). Furthermore, we alsosolved the structure of compound 4, which contained twoaxial OH groups with slight disorder in one of the meso-sub-stituted phenyl rings (see the Supporting Information, S36and S37). Because of poor data quality, we could not locatethe hydrogen atom of the axial OH group. The P�N and(average 1.83 �) and P�O bond lengths (average 1.66 �)were almost in the same range as those observed in com-pound 1.

Absorption, electrochemical, and fluorescence studies : Theabsorption spectra of compounds 1–7 and compound IIIwere recorded in two different coordinating solvents:MeOH and THF (Table 2). A comparison of the absorptionspectra of compounds 1 and III in THF is shown in Figure 5.In general, PV–meso-tetraarylporphyrins[10] show 2–3 weakabsorption bands in the Q-band region and one strong sharpSoret band. However, PV–meso-triarylcorroles exhibited dif-ferent absorption features compared to PV–meso-tetraaryl-porphyrins. As shown in Figure 5, compounds 1–7 exhibitedstrong Soret bands, like compound III, that were eitherbroad or with a small shoulder. However, unlike compoundIII, compounds 1–7 showed an intense band at about600 nm along with 3–4 other Q-bands. This band at about600 nm was much more intense than the Q-band of com-pound III. Thus, the intense band in the visible region ofcomplexes 1–7 is of potential use in materials and medicinalapplications. Furthermore, the absorption bands of com-pounds 1–7 were blue-shifted compared to compound III.There were also significant changes in the absorption fea-tures of compounds 1–7 in terms of their band-position and-intensity depending on the solvent used.

The electrochemical properties of PV–corroles 1–7 weredetermined by cyclic voltammetry and by differential pulsevoltammetry at a scan rate of 50 mV s�1 with tetrabutylam-monium perchlorate (TBAP) as the supporting electrolytein MeCN. The representative first oxidation and reductionwaves for compound 1, along with their differential pulsevoltammograms, are shown in Figure 6 and the data aregiven in Table 3. The electrochemical properties of the PV

complex of meso-triarylcorrole II (Scheme 1), as studied byGross and co-workers, showed one oxidation peak at 1.05 Vand one reduction peak at �1.05 V.[9c] However, all of ourcompounds (1–7) exhibited two oxidation peaks and threereduction peaks. The first oxidation and reduction peakswere reversible in nature whereas the other oxidation andreduction waves were quasi-reversible or irreversible. Com-pared to compound II, compounds 1–7 were easier to oxi-

Figure 4. Three orthogonal views of the ORTEP of compound 1. Ellip-soids are set at 50% probability.

Table 1. Crystallographic data for compound 1.

Parameters [P ACHTUNGTRENNUNG(TPC) ACHTUNGTRENNUNG(OCH3)2] (1)

formula C39H29N4O2P1

Mw 616.64crystal system orthorhombicspace group P21

a [�] 8.3816(4)b [�] 9.5266(6)c [�] 37.694(2)V [�3] 3009.8(3)Z 8m [mm�1] 0.1361calcd [gcm�3] 1.361F ACHTUNGTRENNUNG(000) 12882q range [8] 3.28–25.00e data (Rint) 22842/5261R1, wR2 [I>2s(I)] 0.0445, 0.0844R1, wR2 (all data) 0.0684, 0.0895GOF 0.929Largest diff. peak/hole, [e��3] 0.241/�0.208

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dize but more-difficult to reduce (Table 3). For example,compounds 1–7 exhibited a first oxidation in the range 0.6–0.8 V and a first reduction in the range �1.0 to �1.4 V, de-pending on the meso substituents. Furthermore, it is well es-tablished that, for porphyrins[16] and related macrocycles, thefirst oxidation and reduction peaks correspond to the re-moval or addition of an electron from the frontier orbitalsof the p-system, and that the potential difference (DEred�ox =

Ered�Eox) between them is very similar for a given series ofcompounds, thus corresponding to the HOMO–LUMOenergy gap. The HOMO–LUMO energy gap, along withother information, gives fundamental information about theredox processes in terms of whether the oxidations and re-

ductions are metal-centered or macrocycle-centered. TheHOMO–LUMO gap has been used to distinguish betweenmetal- and corrole-centered redox processes in many redox-active transition-metal complexes of corroles, and it hasbeen suggested that if the gap is about 2.0 V, the corrolemacrocycle is involved in the redox processes but if the gapis significantly less than 2.0 V, then the metal is also in-volved in the redox processes.[17] Because the gaps for com-

Table 2. Absorption data recorded in THF and CH3OH.

Compound Absorption dataIn THF In CH3OH

Soret band[nm]ACHTUNGTRENNUNG(log e)

Q band[nm]ACHTUNGTRENNUNG(log e)

Soret band[nm]ACHTUNGTRENNUNG(log e)

Q-band[nm]ACHTUNGTRENNUNG(log e)

1 411 (5.34) 508 (sh), 407 (5.41) 505 (sh),421 (5.21) 525 (3.97), 414 (5.36) 521 (3.96),

554 (sh), 547 (sh),564 (4.19), 559 (4.13),603 (4.59) 594 (4.60)

III 417 (4.74) 512 (3.71), 424 (5.56) 514 (3.38),427 (4.92) 556 (3.82), 554 (4.12),

597 (3.46) 595 (3.49)

2 422 (5.31) 510 (3.70), 416 (5.35) 504 (sh),530 (3.90), 525 (3.95),567 (4.03), 550 (sh),604 (4.55) 562 (4.06),

596 (4.58)

3 410 (5.49) 515 (sh), 409 (5.38) 508 (3.75),424 (5.05) 526 (4.09), 417 (5.30) 523 (3.92),

555 (sh), 560 (4.08),567 (4.36), 599 (4.62)608 (4.41)

4 414 (5.36) 509 (sh), 409 (5.48) 503 (sh),422 (5.28) 527 (3.97), 414 (5.44) 522 (4.00),

556 (sh), 547 (sh),567 (4.16), 560 (4.16),603 (4.83) 594 (4.68)

5 415 (5.51) 509 (sh), 410 (5.61) 505 (sh),422 (5.45) 527 (4.11), 414 (5.57) 522 (4.12),

555 (sh), 548 (sh),566 (4.28), 560 (4.27),603 (4.83) 595 (4.80)

6 422 (5.01) 535 (4.01), 418 (5.17) 529 (4.06),568 (4.10), 563 (4.12),610 (4.59) 601 (4.66)

7 418 (5.36) 508 (sh), 413 (5.43) 502 (sh),528 (4.04), 523 (4.02),554 (sh), 547 (sh),567 (4.19), 561 (4.17),601 (4.69) 593 (4.65)

Figure 5. Comparison of the Q-band and Soret-band spectra (inset) ofcompounds 1 (solid line) and III (dotted line) in THF; the concentrationsused for the Soret bands were 10�6

m and for the Q bands were 10�5m.

Figure 6. Cyclic voltammogram and differential pulse voltammogram ofcompound 1 in CH3CN using tetrabutylammonium perchlorate (TBAP)as a supporting electrolyte at a scan rate of 50 mV s�1.

Table 3. Redox data recorded in CH3CN.

Compound Oxidation[V]

Reduction[V]

HOMO–LUMO gapACHTUNGTRENNUNG(DEred�ox) [V]

1 0.72, 1.22 �1.41, �1.69, �2.07 2.132 0.77, 1.38 �1.26, �1.66, �1.73 2.033 0.57, 1.08 �1.45, �1.74, �2.15 2.024 0.69, 1.26 �1.37, �1.72, �1.99 2.065 0.69, 1.26 �1.36, �1.70, �1.96 2.056 0.80, 1.38 �1.12, �1.62, �1.90 1.927 0.79, 1.37 �1.11, �1.74 1.90II 1.05 �1.05 2.10

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A. Ghosh and M. Ravikanth

pounds 1–7 were about 2.0 V, we concluded that only thecorrole ring was involved in the redox processes of com-pounds 1–7.

The fluorescence properties of compounds 1–7 and com-pound III were studied by both steady-state and time-re-solved fluorescence techniques. In general, it is well-estab-lished that main-group metallocorroles are strongly fluores-cent with higher quantum yields than their analogous por-phyrins derivatives. It is inferred from the photophysicalstudies of various metallocorroles that GaIII and AlIII com-plexes[8a,18] are brightly fluorescent and exhibit high quan-tum yields (F =0.37–0.76). A comparison of the fluores-cence spectra of compound 1 with its close analogue, com-pound III, in THF at the same concentrations is shown inFigure 7 and the relevant photophysical data are given in

Table 4. This comparison revealed the following: 1) com-pounds 1–7 exhibited a very strong fluorescence band atabout 600 nm, with shoulder bands that were hypsochromi-cally shifted compared to compound III ; 2) compounds 1–7were brightly fluorescent, with high quantum yields (F =

0.33–0.68), compared to the weakly fluorescent compoundIII (F= 0.08); 3) the quantum yield of compound 5 was no-tably low, owing to the heavy halogen-atom effect, which in-creased the intersystem-crossing processes.[19] The quantumyields of compounds 6 and 7 were lowered because of thenitro group, which is also known to significantly quenchfluorescence through a spin-orbit-coupling mechanism thatenhances the intersystem-crossing rates.[19] More-detailedstudies are required to understand the photophysical proper-ties of compounds 6 and 7. Thus, the steady-state-fluores-cence measurements indicated that PV–meso-triarylcorroleswere as brightly fluorescent as AlIII- and GaIII–corroles,which are the best-known fluorescent compounds amongoligopyrrolic macrocycles. The high fluorescence yields ob-served for these PV–meso-triarylcorroles could be rational-ized on the basis that they were structurally rigid hexa-coor-dinated complexes, which decreased the probability of non-radiative-decay pathways, and also because of their more-planar structures, which enhanced the radiative-decay path-

ways, thereby resulting in high fluorescence yields. Time-cor-related single-photon-counting measurements of the fluores-cence lifetimes (t) of compounds 1–4 were performed intwo different solvents and the data are given in Table 4. Thefluorescence decays of compounds 1–4 were fitted toa single exponential in both solvents and the representativefluorescence-decay profile for compound 1 in THF is shownin Figure 8. The singlet-state lifetimes of compounds 1–4were in the range 1.9–3.7 ns. Compound 2, which showedthe highest quantum yield (F= 0.68), exhibited the highestsinglet-state lifetime of about 3.7 ns. We are currently inves-

Figure 7. Comparison of fluorescence spectra of compounds 1 (dottedline) and III (solid line) in THF; the compounds were excited at theircorresponding absorption maxima and the concentrations of the solutionswere about 10�7

m.

Table 4. Emission data recorded in THF and CH3OH.

Compound In THF In CH3OHlem

[nm]Quantumyield

t

[ns]lem

[nm]Quantumyield

t

[ns]

1 572 (sh) 0.48 2.92 600 0.44 3.01610 656 (sh)667 (sh)

2 615 0.62 3.37 605 0.68 3.69670 (sh) 661 (sh)

3 579 (sh) 0.38 2.10 609 0.43 2.26618 664 (sh)675 (sh)

4 573 (sh) 0.33 1.95 601 0.40 2.14610 656 (sh)668 (sh)

5 573 (sh) 0.06 – 602 0.07 –611 658 (sh)669 (sh)

6 579 (sh) 0.30 – 605 0.007 –625 654 (sh)688 (sh)

7 571 (sh) 0.04 – 600 0.005 –606 656 (sh)664 (sh)

Figure 8. Fluorescence-decay profile and the corresponding weighted re-sidual-distribution fit of the fluorescence decay of compound 1 in THF.The excitation wavelength was 406 nm and emissions were detected atthe emission-peak maxima of compound 1 in THF.

Chem. Eur. J. 2012, 18, 6386 – 6396 � 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.chemeurj.org 6393

FULL PAPERHighly Fluorescent Phosphorus(V)–meso-Triarylcorroles

tigating the excited-state dynamics of these PV complexes ofmeso-triarylcorroles.

Conclusion

We have prepared a series of PV complexes of meso-triaryl-corroles and characterized them by using various spectro-scopic techniques. Detailed NMR spectroscopic studies indi-cated that the PV–meso-triarylcorroles preferentially existedin hexacoordinate environments in coordinating solvents(CH3OH, THF, DMSO, etc.) and dissociated to their penta-coordinate complexes in non-coordinating solvents, (toluene,CH2Cl2, and CHCl3). X-ray crystal data for two complexesconfirmed the hexacoordinate geometry of the PV–meso-tri-arylcorroles. Their optical and electrochemical propertieswere very interesting and distinct compared to PV–meso-tet-raarylporphyrins. Unlike PV–meso-tetraarylporphyrins, thePV–meso-triarylcorroles were very brightly fluorescent withhigh quantum yields, and will be very useful for various mo-lecular device applications.

Experimental Section

Chemicals : All chemicals and solvents were purchased from S.D. FineChemicals (India). Column chromatography was performed on silica geland basic alumina that were obtained from Sisco Research Laboratories(India). Tetrabutylammonium perchlorate was purchased from Fluka andused without further purification. All NMR solvents were used as re-ceived. CH2Cl2, THF, and n-hexane were purified and distilled accordingto standard procedures.

Instrumentation : 1H and 31P{1H} NMR spectra were recorded ona Bruker AVANCE III 400 MHz spectrometer. Tetramethylsilane (TMS)was used as an internal reference for the 1H NMR spectra (residualproton; d=7.26 ppm in CDCl3) and 85% H3PO4 was used as an externalreference for the 31P NMR spectra (CDCl3 and CD3OD). HRMS was per-formed on a Q-Tof micromass spectrometer. Absorption and steady-statefluorescence spectra were obtained on Perkin–Elmer Lambda-35 and ISS(US) PC1 Photon-Counting spectrofluorometers, respectively. The fluo-rescence quantum yield (Ff) of PV meso-triaryl corroles 1–7 were estimat-ed from their emission and absorption spectra by using the comparativemethod[20] with [H2 ACHTUNGTRENNUNG(TPP)] as a standard (Ff = 0.11). Time-resolved fluo-rescence-decay measurements were carried out at the magic angle byusing a picosecond-diode-laser-based time-correlated single-photon-counting (TCSPC) fluorescence spectrometer from IBH (UK). All decaycurves were fitted to single exponential functions by using IBH software.Cyclic voltammetry (CV) and differential pulse voltammetry (DPV)were carried out with a BAS electrochemical system by utilizing a three-electrode configuration that consisted of a glassy carbon working elec-trode, a platinum wire auxiliary electrode, and a saturated calomel refer-ence electrode. The experiments were performed in dry MeCN with 0.1 m

tetrabutylammonium perchlorate as the supporting electrolyte.

X-ray crystallography : Single-crystal X-ray analysis of compounds 1 and4 were performed on a CCD Oxford Diffraction XCALIBUR-S diffrac-tometer that was equipped with an Oxford Instruments low-temperatureattachment. Data were collected at 293(2) for compound 1 and at150(2) K for compound 4 using graphite-monochromated MoKa radiation(la = 0.71073 �). The strategy for data collection was evaluated by usingthe CrysAlisPro CCD software. The data were collected by the standardphi-omega scan techniques, and were scaled and reduced by using CrysA-lisPro RED software. The structures were solved by direct methods usingSHELXS-97 and refined by full-matrix least-squares with SHELXL-97,

refining on F2.[21] The positions of all the atoms were obtained by directmethods. All non-hydrogen atoms were refined anisotropically. The re-maining hydrogen atoms were placed in geometrically constrained posi-tions and refined with isotropic temperature factors, typically 1.2Ueq oftheir parent atoms.

CCDC-837991 (1) and CCDC-837992 (4) contain the supplementary crys-tallographic data for this paper. These data can be obtained free ofcharge from The Cambridge Crystallographic Data Centre viawww.ccdc.cam.ac.uk/data_request/cif.

General synthesis : Free-base meso-triarylcorroles were synthesized ac-cording to literature procedures.[22] Phosphorus derivatives 1–7 were syn-thesized by heating a solution of the corresponding free-base meso-triar-ylcorrole in pyridine at reflux in the presence of excess POCl3 (abouta 100-fold excess).

Synthesis of compound 1: To a solution of 5,10,15-triphenylcorrole(100 mg, 0.189 mmol) in dry pyridine (10 mL) was added POCl3 (1.8 mL,19.25 mmol) and the reaction mixture was heated to reflux for 15 minunder a nitrogen atmosphere. The solution immediately changed froma deep green color to a purple-violet color with a greenish tint. The prog-ress of reaction was monitored by TLC analysis and its completion wasdetermined by absorption spectroscopy. After completion of reaction, thesolvent was evaporated under reduced pressure. The crude solid was sub-jected to column chromatography on basic alumina and the desired com-pound was collected from a greenish pink-violet-colored band by elutingwith CH2Cl2. The solvent was removed on a rotary evaporator to afforda deep purple-violet solid. The compound was recrystallized fromCH2Cl2/n-hexane (1:3) to afford compound 1 as a purple solid in 78 %yield (87 mg, 0.148 mmol). 1H NMR (400 MHz, CD3OD): d=9.38 (dd, 3J-ACHTUNGTRENNUNG(H,H) =4.4 Hz, 4J ACHTUNGTRENNUNG(P,H)=2.6 Hz, 2H; b-pyrrole H), 9.03 (dd, 3J ACHTUNGTRENNUNG(H,H) =

4.9 Hz, 4J ACHTUNGTRENNUNG(P,H)=3.6 Hz, 2H; b-pyrrole H), 8.95 (dd, 3J ACHTUNGTRENNUNG(H,H) =4.4 Hz, 4J(P,H)=3.4 Hz, 2 H; b-pyrrole H), 8.78 (dd, 3J ACHTUNGTRENNUNG(H,H) =4.9 Hz, 4J ACHTUNGTRENNUNG(P,H)=

3.0 Hz, 2H; b-pyrrole H), 8.25–8.28 (m, 4H; Ar H), 8.15–8.17 (m, 2H;Ar H), 7.78–7.87 ppm (m, 9 H; Ar H); 31P{1H} NMR (400 MHz,CD3OD): d=�178.03 ppm; HRMS: m/z : 571.1697 [M�17]+.

Compounds 2–7 were prepared by following the same synthetic routementioned for compound 1.

Compound 2 : Compound 2 was obtained as a pink-violet solid in 80%yield (88 mg, 0.132 mmol). 1H NMR (400 MHz, CD3OD): d=9.43 (dd, 3J-ACHTUNGTRENNUNG(H,H) =4.4 Hz, 4J ACHTUNGTRENNUNG(P,H)=2.4 Hz, 2H; b-pyrrole H), 9.02 (dd, 3J ACHTUNGTRENNUNG(H,H) =

4.8 Hz, 4J ACHTUNGTRENNUNG(P,H)=3.7 Hz, 2H; b-pyrrole H), 8.96 (dd, 3J ACHTUNGTRENNUNG(H,H) =4.4 Hz, 4J(P,H)=3.4 Hz, 2 H; b-pyrrole H), 8.77 (dd, 3J ACHTUNGTRENNUNG(H,H) =5.0 Hz, 4J ACHTUNGTRENNUNG(P,H)=

2.9 Hz, 2 H; b-pyrrole H), 8.34–8.46 (m, 5 H; Ar H), 8.15–8.21 ppm (m,7H; Ar H); 31P{1H} NMR (400 MHz, CD3OD): d =�184.79 ppm;HRMS: m/z : 646.1515 [M�17]+.

Compound 3 : Compound 3 was obtained as a dark violet solid in 75 %yield (82 mg, 0.121 mmol). 1H NMR (400 MHz, CD3OD): d=9.34 (dd, 3J-ACHTUNGTRENNUNG(H,H) =4.4 Hz, 4J ACHTUNGTRENNUNG(P,H)=2.6 Hz, 2H; b-pyrrole H), 9.03 (dd, 3J ACHTUNGTRENNUNG(H,H) =

4.8 Hz, 4J ACHTUNGTRENNUNG(P,H) =3.7 Hz, 2H; b-pyrrole H), 8.94 (dd superimposed, J=

4.0 Hz, 2H; b-pyrrole H), 8.77 (dd, 3J ACHTUNGTRENNUNG(H,H) =4.9 Hz, 4J ACHTUNGTRENNUNG(P,H) =3.0 Hz,2H; b-pyrrole H), 8.52–8.54 (m, 2H; Ar H), 8.16–8.18 (m, 3H; Ar H),8.04–8.06 (m, 2H; Ar H), 7.78–7.87 (m, 1 H; Ar H), 7.33–7.45 (m, 4H;Ar H), 4.06–4.08 ppm (m, 9 H, OCH3); 31P{1H} NMR (400 MHz,CD3OD): d=�178.08 ppm; HRMS: m/z : 679.2129 [M]+.

Compound 4 : Compound 4 was obtained as a dark violet solid in 81 %yield (89 mg, 0.128 mmol). 1H NMR (400 MHz, CD3OD): d=9.42 (dd, 3J-ACHTUNGTRENNUNG(H,H) =4.4 Hz, 4J ACHTUNGTRENNUNG(P,H)=2.6 Hz, 2H; b-pyrrole H), 9.05 (dd, 3J ACHTUNGTRENNUNG(H,H) =

5.0 Hz, 4J ACHTUNGTRENNUNG(P,H) =3.6 Hz, 2H; b-pyrrole H), 8.97 (dd, 3J ACHTUNGTRENNUNG(H,H) =4.4 Hz, 4J-ACHTUNGTRENNUNG(P,H)=3.5 Hz, 2 H; b-pyrrole H), 8.80 (dd, 3J ACHTUNGTRENNUNG(H,H) =4.9 Hz, 4J ACHTUNGTRENNUNG(P,H)=

3.0 Hz, 2H; b-pyrrole H), 8.52–8.54 (m, 1H; Ar H), 8.12–8.14 (m, 3H;Ar H), 8.23–8.25 (m, 2H; Ar H), 7.80–7.87 (m, 5H; Ar H), 7.42–7.45 ppm (m, 1H; Ar H); 31P{1H} NMR (400 MHz, CD3OD): d=

�177.89 ppm; HRMS: m/z : 692.0707 [M+1]+.

Compound 5. Compound 5 was obtained as a dark blue-violet solid in79% yield (85 mg, 0.103 mmol). 1H NMR (400 MHz, CD3OD): d=9.43(dd, 3J ACHTUNGTRENNUNG(H,H) =4.5 Hz, 4J ACHTUNGTRENNUNG(P,H)=2.5 Hz, 2 H; b-pyrrole H), 9.06 (dd, 3J-ACHTUNGTRENNUNG(H,H) =5.0 Hz, 4J ACHTUNGTRENNUNG(P,H)=3.6 Hz, 2H; b-pyrrole H), 8.99 (dd, 3J ACHTUNGTRENNUNG(H,H) =

4.5 Hz, 4J ACHTUNGTRENNUNG(P,H) =2.9 Hz, 2H; b-pyrrole H), 8.81 (dd, 3J ACHTUNGTRENNUNG(H,H) =5.0 Hz, 4J-

www.chemeurj.org � 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Eur. J. 2012, 18, 6386 – 63966394

A. Ghosh and M. Ravikanth

ACHTUNGTRENNUNG(P,H)=3.0 Hz, 2H; b-pyrrole H), 8.52–8.54 (m, 1H; Ar H), 8.17–8.19 (m,4H; Ar H), 7.89–8.01 (m, 7H; Ar H); 31P{1H} NMR (400 MHz, CD3OD):d=�177.88 ppm; HRMS: m/z : 823.9159 [M+1]+.

Compound 6 : Compound 6 was obtained as a dark-blue solid in 77%yield (84 mg, 116 mmol). 1H NMR (400 MHz, CD3OD): d=9.46 (dd, 3J-ACHTUNGTRENNUNG(H,H) =4.5 Hz, 4J ACHTUNGTRENNUNG(P,H)=2.5 Hz, 2H; b-pyrrole H), 9.07 (dd, 3J ACHTUNGTRENNUNG(H,H) =

5.0 Hz, 4J ACHTUNGTRENNUNG(P,H) =3.6 Hz, 2H; b-pyrrole H), 9.01 (dd, 3J ACHTUNGTRENNUNG(H,H) =4.4 Hz, 4J-ACHTUNGTRENNUNG(P,H)=3.4 Hz, 2 H; b-pyrrole H), 8.83 (dd, 3J ACHTUNGTRENNUNG(H,H) =5.0 Hz, 4J ACHTUNGTRENNUNG(P,H)=

2.9 Hz, 2H; b-pyrrole H), 8.67–8.74 (m, 4H; Ar H), 8.44–8.54 (m, 5H;Ar H), 7.83–7.87 (m, 1 H; Ar H), 7.42–7.45 ppm (m, 2 H; Ar H);31P{1H} NMR (400 MHz, CD3OD): d=�184.68 ppm; HRMS: m/z :706.1262 [M�17]+.

Compound 7: Compound 7 was obtained as a blue-violet solid in 78 %yield (85 mg, 0.117 mmol). 1H NMR (400 MHz, CD3OD): d=9.46 (dd, 3J-ACHTUNGTRENNUNG(H,H) =4.5 Hz, 4J ACHTUNGTRENNUNG(P,H)=2.4 Hz, 2H; b-pyrrole H), 9.11 (br s, 2 H, b-pyr-role H), 9.04 (dd, 3J ACHTUNGTRENNUNG(H,H) =5.0 Hz, 4J ACHTUNGTRENNUNG(P,H)=3.6 Hz, 2 H; b-pyrrole H),8.98 (dd, 3J ACHTUNGTRENNUNG(H,H) =4.4 Hz, 4J ACHTUNGTRENNUNG(P,H)= 3.5 Hz, 2H; b-pyrrole H), 8.80 (dd,3J ACHTUNGTRENNUNG(H,H) =5.0 Hz, 4J ACHTUNGTRENNUNG(P,H) =2.9 Hz, 2H; b-pyrrole H), 8.62–8.71 (m, 4H;Ar H), 8.51–8.57 (m, 3H; Ar H), 8.04–8.12 (m, 2 H; Ar H), 7.83–7.87 (m,1H; Ar H), 7.41–7.45 ppm (m, 2 H; Ar H); 31P{1H} NMR (400 MHz,CD3OD): d=�184.76 ppm; HRMS: m/z : 724.1371 [M]+.

Acknowledgements

M.R. thanks the Department of Atomic Energy, Government of India,for their financial support and A.G. thanks the CSIR, India for a fellow-ship. The authors also thank Shaikh M. Mobin, National Single-CrystalX-ray Diffraction Facility, IIT Bombay (India).

[1] a) I. Aviv, Z. Gross, Chem. Commun. 2007, 1987; b) L. Flamigni,D. T. Gryko, Chem. Soc. Rev. 2009, 38, 1635; c) D. T. Gryko, J. Por-phyrins Phthalocyanines 2008, 12, 906; d) S. Nardis, D. Monti, R.Paolesse, Mini-Rev. Org. Chem. 2005, 2, 355; e) R. Paolesse, Synlett2008, 15, 2215; f) D. T. Gryko, Eur. J. Org. Chem. 2002, 1735; g) Z.Gross, H. B. Gray, Adv. Synth. Catal. 2004, 346, 165; h) J. F. B.Barata, M. G. P. M. S. Neves, A. C. Tome, J. A. S. Cavaleiro, J. Por-phyrins Phthalocyanines 2009, 13, 415; i) D. T. Gryko, J. P. Fox, D. P.Goldberg, J. Porphyrins Phthalocyanines 2004, 8, 1091; j) D. P. Gold-berg, Acc. Chem. Res. 2007, 40, 626; k) A. W. Johnson, I. T. Kay, J.Chem. Soc. 1965, 1620; l) N. S. Genokhova, T. A. Melent’eva, V. M.Berezovskii, Russ. Chem. Rev. 1980, 49, 1056; m) T. A. Melent’eva,Russ. Chem. Rev. 1983, 52, 641; n) C. Erben, S. Will, K. M. Kadish inThe Porphyrin Handbook Vol. 2, (Eds.: K. M. Kadish, K. M. Smith,R. Guilard), Academic Press, Burlington, MA, 2000, p. 233; o) R.Paolesse in The Porphyrin Handbook Vol. 2, (Eds.: K. M. Kadish,K. M. Smith, R. Guilard), Academic Press, Burlington, MA, 2000,p. 201; p) S. Licoccia, R. Paolesse, Struct. Bonding (Berlin) 1995, 84,71.

[2] a) T. Ding, E. A. Alem�n, D. A. Modarelli, C. J. Ziegler, J. Phys.Chem. A 2005, 109, 7411; b) B. Ventura, A. D. Esposti, B. Koszarna,D. T. Gryko, L. Flamigni, New J. Chem. 2005, 29, 1559; c) J. H.Palmer, A. C. Durrell, Z. Gross, J. R. Winkler, H. B. Gray, J. Am.Chem. Soc. 2010, 132, 9230; d) J. Vestfrid, M. Botoshansky, J. H.Palmer, A. C. Durrell, H. B. Gray, Z. Gross, J. Am. Chem. Soc.2011, 133, 12899; e) J. H. Palmer, M. W. Day, A. D. Wilson, L. M.Henling, Z. Gross, H. B. Gray, J. Am. Chem. Soc. 2008, 130, 7786;f) J. H. Palmer, A. Mahammed, K. M. Lancaster, Z. Gross, H. B.Gray, Inorg. Chem. 2009, 48, 9308; g) J. Poulin, C. Stern, R. Guilard,P. D. Harvey, Photochem. Photobiol. 2006, 82, 171.

[3] a) Z. Gross, N. Galili, I. Saltsman, Angew. Chem. 1999, 111, 1530;Angew. Chem. Int. Ed. 1999, 38, 1427; b) Z. Gross, N. Galili, L. Sim-khovich, I. Saltsman, M. Botoshansky, D. Blaser, R. Boese, I. Gold-berg, Org. Lett. 1999, 1, 599.

[4] R. Paolesse, L. Jaquinod, D. J. Nurco, S. Mini, F. Sagoni, T. Boschi,K. M. Smith, Chem. Commun. 1999, 1307.

[5] a) Z. Gross, J. Biol. Inorg. Chem. 2001, 6, 733; b) Z. Gross, H. B.Gray, Comments Inorg. Chem. 2006, 27, 61; c) D. Walker, S. Chap-pel, A. Mahammed, J. J. Weaver, B. S. Brunschwig, J. R. Winkler,H. B. Gray, A. Zaban, Z. Gross, J. Porphyrins Phthalocyanines 2006,10, 1259; d) D. Aviezer, S. Cotton, M. David, A. Segev, N. Khaselev,N. Galili, Z. Gross, A. Yayon, Cancer Res. 2000, 60, 2973; e) A. Ma-hammed, Z. Gross, Dalton Trans. 2010, 39, 2998; f) I. Saltsman, I.Goldberg, Z. Gross, Tetrahedron Lett. 2003, 44, 5669; g) H. Agadja-nian, J. J. Weaver, A. Mahammed, A. Rentsendorj, S. Bass, J. Kim,I. J. Dmochowski, R. Margalit, H. B. Gray, Z. Gross, L. K. Medina-Kauwe, Pharm. Res. 2006, 23, 367; h) A. Mahammed, Z. Gross, J.Am. Chem. Soc. 2005, 127, 2883; i) A. Mahammed, Z. Gross, Chem.Commun. 2010, 46, 7040; j) A. Mahammed, Z. Gross, Angew. Chem.2006, 118, 6694; Angew. Chem. Int. Ed. 2006, 45, 6544; k) M. Ecksh-tain, I. Zilbermann, A. Mahammed, I. Saltsman, Z. Okun, E.Maimon, H. Cohen, D. Meyersteinc, Z. Gross, Dalton Trans. 2009,7879; l) Z. Okun, L. Kupershmidt, T. Amit, S. Mandel, O. Bar-Am,M. B. H. Youdim, Z. Gross, ACS Chem. Biol. 2009, 4, 910; m) J.Youn Hwang, H. Agadjanian, L. K. Medina-Kauwe, Z. Gross, H. B.Gray, K. Sorasaenee, D. L. Farkas, Prog. Biomed. Opt. Imaging2008, 6859, 68590G; n) H. Agadjanian, J. Ma, A. Rentsendorj, V.Valluripalli, J. Y. Hwang, A. Mahammed, D. L. Farkas, H. B. Gray,Z. Gross, L. K. Medina-Kauwe, Proc. Natl. Acad. Sci. USA 2009,106, 6105; o) I. Aviv-Harel, Z. Gross, Chem. Eur. J. 2009, 15, 8382.

[6] a) A. Ghosh, T. Wondimagegn, A. B. J. Parusel, J. Am. Chem. Soc.2000, 122, 5100; b) A. Ghosh, E. Steene, J. Biol. Inorg. Chem. 2001,6, 740; c) G. Golubkov, J. Bendix, H. B. Gray, A. Mahammed, I.Goldberg, A. J. DiBilio, Z. Gross, Angew. Chem. 2001, 113, 2190;Angew. Chem. Int. Ed. 2001, 40, 2132; d) I. H. Wasbotten, T. Wondi-magegn, A. Ghosh, J. Am. Chem. Soc. 2002, 124, 8104; e) Z. Gross,L. Simkhovich, N. Galili, Chem. Commun. 1999, 599; f) Z. Gross, G.Golubkov, L. Simkhovich, Angew. Chem. 2000, 112, 4211; Angew.Chem. Int. Ed. 2000, 39, 4045; g) A. E. Meier-Callahan, A. J. Di Bi-lio, L. Simkhovich, A. Mahammed, I. Goldberg, H. B. Gray, Z.Gross, Inorg. Chem. 2001, 40, 6788; h) L. Simkhovich, Z. Gross, Tet-rahedron Lett. 2001, 42, 8089; i) J. Bendix, I. J. Dmochowski, H. B.Gray, A. Mahammed, L. Simkhovich, Z. Gross, Angew. Chem. 2000,112, 4214; Angew. Chem. Int. Ed. 2000, 39, 4048.

[7] a) Y. Murakami, Y. Matsuda, S. Yamada, J. Chem. Soc. DaltonTrans. 1981, 855; b) Y. Matsuda, S. Yamada, K. Murakami, Inorg.Chem. 1992, 31, 2305; c) E. Vogel, S. Will, A. S. Tilling, L. Neumann,J. Lex, E. Bill, A. X. Trautwein, K. Wieghardt, Angew. Chem. 1994,106, 771; Angew. Chem. Int. Ed. Engl. 1994, 33, 731; d) S. Will, J.Lex, E. Vogel, V. A. Adamian, E. V. Caemelbecke, K. M. Kadish,Inorg. Chem. 1996, 35, 5577; e) E. V. Caemelbecke, S. Will, M.Autret, V. A. Adamian, J. Lex, J. P. Gisselbrecht, M. Gross, E.Vogel, K. M. Kadish, Inorg. Chem. 1996, 35, 184; f) M. Autret, S.Will, E. V. Caemelbecke, J. Lex, J. P. Gisselbrecht, M. Gross, E.Vogel, K. M. Kadish, J. Am. Chem. Soc. 1994, 116, 9141; g) S. Will,J. Lex, E. Vogel, H. Schmickler, J. P. Gisselbrecht, C. Haubtmann,M. Bernard, M. Gross, Angew. Chem. 1997, 109, 367; Angew. Chem.Int. Ed. Eng. 1997, 36, 357; h) K. M. Kadish, V. A. Adamian, E. V.Caemelbecke, E. Gueletii, S. Will, C. Erben. E. Vogel, J. Am. Chem.Soc. 1998, 120, 11986; i) J. Bendix, G. Golubkov, H. B. Gray, Z.Gross, Chem. Commun. 2000, 1957; j) S. Cai, F. A. Walker, S. Licoc-cia, Inorg. Chem. 2000, 39, 3466; k) S. Licoccia, E. Morgante, R.Paolesse, F. Polizio, M. O. Senge, E. Tondello, T. Boschi, Inorg.Chem. 1997, 36, 1564; l) K. E. Thomas, I. H. Wasbotten, A. Ghosh,Inorg. Chem. 2008, 47, 10469; m) B. O. Roos, V. Veryazov, J. Conra-die, P. R. Taylor, A, Ghosh, J. Phys. Chem. B 2008, 112, 14099;n) K. E. Thomas, J. Conradie, L. K. Hansen, A. Ghosh, Inorg.Chem. 2011, 50, 3247.

[8] a) I. Aviv-Harel, Z. Gross, Coord. Chem. Rev. 2011, 255, 717; b) R.Paolesse, S. Licoccia, T. Boschi, Inorg. Chim. Acta 1990, 178, 9;c) J. W. Buchler, K. L. Lay, Inorg. Nucl. Chem. Lett. 1974, 10, 297;d) T. Barbour, W. J. Belcher, P. J. Brothers, C. E. F. Rickard, D. C.Ware, Inorg. Chem. 1992, 31, 746; e) L. M. Reith, M. Stiftinger, U.Monkowius, G. Knçr, W. Schoefberger, Inorg. Chem. 2011, 50, 6788;f) S. Licoccia, R. Paolesse, E. Tassoni, F. Poliziob, T. Boschi, Chem.

Chem. Eur. J. 2012, 18, 6386 – 6396 � 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.chemeurj.org 6395

FULL PAPERHighly Fluorescent Phosphorus(V)–meso-Triarylcorroles

Soc. Dalton Trans. 1995, 3617; g) A. M. Albrett, J. Conradie, P. D. W.Boyd, G. R. Clark, A. Ghosh, P. J. Brothers, J. Am. Chem. Soc. 2008,130, 2888; h) D. Kowalska, X. Liu, U. Tripathy, A. Mahammed, Z.Gross, S. Hirayama, R. P. Steer, Inorg. Chem. 2009, 48, 2670;i) K. M. Kadish, C. Erben, Z. Ou, V. A. Adamian, S. Will, E. Vogel,Inorg. Chem. 2000, 39, 3312; j) K. M. Kadish, S. Will, V. A. Ada-mian, B. Walther, C. Erben, Z. Ou, N. Guo, E. Vogel, Inorg. Chem.1998, 37, 4573.

[9] a) R. Paolesse, T. Boschi, S. Licoccia, R. G. Khouryb, K. M. Smith,Chem. Commun. 1998, 1119; b) K. M. Kadish, Z. Ou, V. A. Ada-mian, R. Guilard, C. P. Gros, C. Erben, S. Will, E. Vogel, Inorg.Chem. 2000, 39, 5675; c) L. Simkhovich, A. Mahammed, I. Gold-berg, Z. Gross, Chem. Eur. J. 2001, 7, 1041.

[10] a) S. Mangani, E. F. Meyer Jr., D. L. Cullen, M. Tsutsui, C. J. Carra-no, Inorg. Chem. 1983, 22, 400; b) C. A. Marrese, C. J. Carrano,Inorg. Chem. 1983, 22, 1858; c) C. J. Carrano, M. Tsutsui, J. Coord.Chem. 1977, 7, 79; d) M. Gouterman, P. Sayer, E. Shankland, J. P.Smith, Inorg. Chem. 1981, 20, 87; e) P. Sayer, M. Gouterman, C. R.Connell, J. Am. Chem. Soc. 1977, 99, 1082.

[11] J. P. Fox, D. P. Goldberg, Inorg. Chem. 2008, 47, 9010, and the refer-ences therein.

[12] a) R. Guilard, A. Zrineh, A. Tabard, A. Endo, B. C. Han, C. Le-comte, M. Souhassou, A. Habbou, M. Ferhat, K. M. Kadish, Inorg.Chem. 1990, 29, 4476; b) A. L. Balch, L. Latos-Grazynski, B. C.Nom, S. L. Phillips, Inorg. Chem. 1993, 32, 1124; c) M. P. Schopfer,B. Mondal, D. H. Lee, A. A. N. Sarjeant, K. D. Karlin, J. Am. Chem.Soc. 2009, 131, 11304; d) R. Timkovich, A. Tulinsky, J. Am. Chem.Soc. 1969, 91, 16; e) V. Mckee, C. A. Rodley, Inorg. Chim. Acta1988, 151, 233.

[13] a) L. Simkhovich, N. Galili, I. Saltsman, I. Goldberg, Z. Gross,Inorg. Chem. 2000, 39, 2704; b) S. Nardis, R. Paolesse, S. Licoccia,F. R. Fronczek, M. G. H. Vicente, T. K. Shokhireva, S. Cai, F. A.Walker, Inorg. Chem. 2005, 44, 7030; c) L. Wagnert, A. Berg, E. Sta-vitski, T. Berthold, G. Kothe, I. Goldberg, A. Mahammed, L. Sim-khovich, Z. Gross, H. Levanon, Appl. Magn. Reson. 2006, 30, 591;d) L. Simkhovich, P. Iyer, I. Goldberg, Z. Gross, Chem. Eur. J. 2002,8, 2595; e) S. Nardis, F. Mandoj, R. Paolesse, F. R. Fronczek, K. M.Smith, L. Prodi, M. Montalti, G. Battistini, Eur. J. Inorg. Chem.

2007, 2345; f) L. Simkhovich, I. Goldberg, Z. Gross, J. Inorg. Bio-chem. 2000, 80, 235.

[14] a) S. Hiroto, I. Hisaki, H. Shinokubo, A. Osuka, Angew. Chem.2005, 117, 6921; Angew. Chem. Int. Ed. 2005, 44, 6763; b) C. P. Gros,J. M. Barbe, E. Espinosa, R. Guilard, Angew. Chem. 2006, 118,5770; Angew. Chem. Int. Ed. 2006, 45, 5642; c) R. Paolesse, A. Mari-nia, S. Nardisa, A. Froiioa, F. Mandoja, D. J. Nurcob, L. Prodic, M.Montaltic, K. M. Smith, J. Porphyrins Phthalocyanines 2003, 7, 25;d) R. Paolesse, S. Nardis, M. Venanzi, M. Mastroianni, M. Russo,F. R. Fronczek, M. G. Vicente, Chem. Eur. J. 2003, 9, 1192; e) R.Du, C. Liu, D. Shen, Q. Chen, Synlett 2009, 2701.

[15] a) A. B. Alemayehu, L. K. Hansen, A. Ghosh, Inorg. Chem. 2010,49, 7608; b) A. B. Alemayehu, E. Gonzalez, L. K. Hansen. A.Ghosh, Inorg. Chem. 2009, 48, 7794; c) N. Y. Edwards, R. A. Eikey,M. I. Loring, M. M. A. -Omar, Inorg. Chem. 2005, 44, 3700.

[16] a) C. A. Marrese, C. J. Carrano, Inorg. Chem. 1984, 23, 3961;b) C. A. Marrese, C. J. Carrano, J. Chem. Soc. Chem. Commun.1982, 1279.

[17] M. Mastroianni, W. Zhu, M. Stefanelli, S. Nardis, F. R. Fronczek,K. M. Smith, Z. Ou, K. M. Kadish, R. Paolesse, Inorg. Chem. 2008,47, 11680, and references therein.

[18] a) A. Mahammed, Z. Gross, J. Inorg. Biochem. 2002, 88, 305; b) X.Liu, A. Mahammed, U. Tripathy, Z. Gross, R. P. Steer, Chem. Phys.Lett. 2008, 459, 113; c) P. J. Brothers, Chem. Commun. 2008, 2090.

[19] a) N. J. Turro, Modern Molecular Photochemistry, Benjamin, MenloPark, 1978 ; b) J. B. Birks, Photophysics of Aromatic Molecules,Wiley Interscience, New York, 1970 ; c) J. R. Lakowicz, Principles ofFluorescence Spectroscopy, Plenum: New York, 1983.

[20] I. Gupta, M. Ravikanth, Inorg. Chim. Acta 2007, 360, 1731.[21] G. M. Sheldrick, Acta Crystallogr. Sect. A 2008, 64, 112; Program for

Crystal Structure Solution and Refinement ; University of Goettingen,Goettingen, Germany, 1997.

[22] B. Koszarna, D. T. Gryko, J. Org. Chem. 2006, 71, 3707.

Received: October 12, 2011Revised: January 27, 2012

Published online: March 30, 2012

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A. Ghosh and M. Ravikanth